Feds roll out details of 54.5 mpg standard

They specify that all new vehicles sold in the U.S. must average the equivalent of 54.5 miles per gallon in 2025, up from 29.7 now and 35.5 mpg by 2016.

It is "a monumental day for the American people," Transportation Secretary Ray LaHood said in announcing that the rules now are final.

The announcement comes as the Republicans open their national convention in Tampa. LaHood several times praised President Obama, a Democrat, for efforts to boost fuel economy and save consumers money.

LaHood said the regulations might boost the price of a new vehicle $1,800 in 2025, but the lower fuel expense could save drivers $8,000 over the life of the cars.

Auto dealers disagree. The National Automobile Dealers Association said the higher mpg standard "will hike the average price of a new vehicle by nearly $3,000 when fully implemented. This increase shuts almost 7 million people out of the new car market entirely and prevents many millions more from being able to afford new vehicles that meet their needs."

What you won't see is anything close to 54.5 mpg on the window sticker of 2025-model cars and trucks.

Why your real-world mileage will vary:

The government mileage rating on the new vehicle window stickers will be in the high 30s to around 40 mpg in combined city/highway driving. The window-sticker mileage rating is arrived at using a formula meant to match real-world driving. By contrast, the federal mileage rule -- so-called CAFE, for corporate average fuel economy -- is based on lab tests for combined city and highway driving.

Automakers, through their lobby group Alliance of Automobile Manufacturers, said: "After years of billion-dollar investments by automakers, consumers have a lot of choice in fuel-efficient cars and light trucks, and automakers are working to sell these high-mileage vehicles in high volumes."

LaHood called such cars "wildly popular."

The category where most high-mileage cars are found -- the group defined as small cars and including everything from the tiny Fiat 500 to the bigger Toyota Corolla compact -- are selling 18.3% faster through July than they were a year ago, according to tallymaster Autodata.

However, that's not a huge lead compared with all new vehicle sales, which are up 14%. And midsize cars are even more popular than small ones, up 21.8% from a year earlier.

"Compliance with higher fuel-economy standards is based on sales," the Alliance said in a statement, drawing a distinction between what buyers will accept and what automakers might be forced to build to meet the tighter regulations.

The Natural Resources Defense Council applauded the final rules.

"We're very happy. This is a good rule, a strong rule. This is the biggest step this country's taken to reduce pollution and our dependence on oil since the original 1970s" Clean Air Act, says Roland Hwang, NRDC's transportation director.

The final rules say the government will review progress in five years. It could revise the regulations, if necessary. "Automakers will be looking for a rigorous midterm review with periodic check-ins since it is difficult to predict three years in advance, let alone 13 years," the Alliance said.

The new regulation isn't strictly a fuel-consumption rule. Rather, it limits the amount of carbon dioxide a vehicle may emit to 163 grams per mile, Hwang noted. The amount of carbon dioxide coming out the tailpipe, however, is directly related to the amount of fuel burned, and translates to the 54.5 mpg standard.

But there are credits automakers can use to reduce the actual laboratory-tested mpg it must achieve. For instance, a credit of as much as 5 mpg is available for making more efficient air conditioning that uses coolant expected to be more benign environmentally than the HFC now used. It, in turn, was expected to have been better than the CFC -- freon -- it replaced in the 1990s.

Vehicles that burn natural gas, or are powered by electricity, count more heavily toward meeting the rule than do conventional gasoline-power vehicles.

Diesels, though fuel-efficient by nature, get no extra credit in the regs. Volkswagen's Passat midsize sedan with a diesel has a window-sticker rating of 35 mpg in combined city/highway driving -- already close to the 38 to 40 mpg average you'd see on many new vehicles in 2025.

Not each new vehicle has to hit the regulatory number. Instead, all the vehicles an automaker sells must average at least the government number. Thus, a company that specialized in small cars would have an easier time reaching an average of 54.5 mpg than a company that sold mostly bigger, heavier vehicles.

The mileage standard for cars gets stricter, faster than for trucks, Environmental Protection Agency Administrator Lisa Jackson noted. Trucks often are work or tow vehicles that need bigger, more fuel-thirsty engines and will be harder to turn into high-mpg vehicles, she acknowledged -- but they eventually must make the shift. "Cars are ramping down faster than trucks, and they catch each other at the end," she said.

If there's any magic in the new regulations, it's the coalition of usually contentious factions that stayed together long enough to get the rule approved. Key player was California, which can invoke its own carbon-emission standards under some circumstances. But on this go-round, California said it wouldn't do that, in order to give the automakers the single, nationwide mpg standard they said was necessary for their planning and engineering.

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About Chris Woodyard

Chris Woodyard is an auto writer for USA TODAY who covers all aspects of motoring. He revels in the exhaust note of a Maserati and the sharp creases of a Cadillac CTS. Chris strives to live a Porsche life on a Scion budget. More about Chris